Andrena rosae in the Zuid-Hollandse Biesbosch (Hymenoptera: Apoidea: Andrenidae)Andrena rosae is a fairly large, black and red mining bee. It has declined dramatically in the 20thcentury in northwestern Europe. In the Netherlands the species only survived in and around theBiesbosch, at the confluence of the rivers Maas and Rijn. In 2005 a research was performed toestablish the distribution pattern within the northern part of the Biesbosch (province of Zuid-Holland). Furthermore, attention was paid to nest locations and pollen gathering. The speciesproved to be quite common throughout the study area. In spring, nests were found on thesouthern slopes of the dikes. Surprisingly, no nests could be found during the summer months.Near the nests unusually large specimens of Nomada fabriciana were found: these might possiblybe parasites of A. rosae. In spring, female A. rosae where seen only on Salix and Prunus spinosa.Pollen analysis indicated that pollen had only been collected on Salix. In summer, femaleswere frequently found on Heracleum sphondylium, Angelica sylvestris, Eryngium campestre andoccasionally (and surprisingly) also on Filipendula ulmaria. Pollen analysis showed that the beesindeed collected pollen on all of these plants.German authors (e.g. Westrich 1989) state that A. rosae occurs only in summer and that thespring specimens belong to another species, A. stragulata (synonym A. eximia). Presently, thismatter is being studied by analysing the dna of Dutch specimens. Details of this dna-analysiswill be published separately.